Quantifying extended RE124 stacking faults in RE123 thin films using x-ray diffraction

Currently most optimizations of the superconducting properties of REBa2Cu3O7-δ (REBCO, RE123) are done based on process parameters. Defect-density based methods offer a more direct way for such optimization due to the fact that the superconducting properties of a REBCO conductor emerge from its defect landscape. In this study, an x-ray diffraction (XRD) method will be presented that helps to determine the stacking fault density (SFD) of REBa2Cu4O8 (RE124) stacking faults reasonably well. It is based on the fact that RE124 stacking faults introduce peak shifts and broadening to (00 l) reflections of RE123. Both quantities vary with the Miller index l, which enables the identification and quantification of these stacking faults. The method is tested using Sm123 thin film samples produced via chemical solution deposition (CSD). A Cu excess is used to facilitate the growth of extended Sm124 stacking faults through a high-temperature oxygenation. The resulting samples show exactly the behavior predicted by the presented theory. The SFDs determined via XRD are then cross-checked by transmission electron microscopy micrographs. It is found that the SFD from peak shift describes the majority of the samples to a sufficient degree of accuracy. ... mehrTherefore, the presented method is applicable to quantify extended Re124 stacking faults in RE123 thin films.